Much of the arable land in Ethiopia is negatively affected by soil acidity and Al-toxicity.
These areas are mainly found in the high rainfall areas of the north western, western, south western and southern parts of the country. Use of lime in the areas affected by acid soils is affected by its local unavailability, its high cost, and the difficulties associated with its transport, and the application of the appropriate tonnages of lime often recommended to offset the of the buffering capacity of the acid soils. On the other hand, competing uses of crop residues for fuel, animal feed and construction material hinders the widespread use of compost and animal manure for soil acidity management. In contrast, Al-tolerant crop varieties can be used as the primary component of an integrated acid soil management strategy for Ethiopia. However, this will need a shift in research priorities to enable the start of active breeding of staple crops for adaptation to the acid soils of Ethiopia, and specifically to tef breeding.
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CHAPTER 2
Soil acidity: Importance, assessment of perceived causes and indicators, coping strategies and implications in cereal based mixed-
farming system of north western Ethiopia Abstract
Soil acidity is one of major crop production constraints in north western Ethiopia.
Nonetheless, information on the extent of soil acidity across land-uses is scarce. A participatory rural appraisal (PRA) was conducted in three Districts of north western Ethiopia affected by acid soils in order to: 1) Assess the state of soil acidity under multiple land-uses; 2) Determine the perceived causes and indicators of soil acidity, and coping strategies of farmers dealing with soil acidity; and 3) Assess the importance of soil acidity as a crop production constraint. Semi- structured interviews, group discussions and soil analyses were the main techniques used to generate data.
Soil samples were collected from five dominant land-uses and were analysed for soil pH, exchangeable acidity and other physico-chemical properties. Farmers’
perceptions were that the causes of soil acidity included: Soil erosion; competing use of local resources and poor nutrient recycling; the abandoning traditional fertility management practices; and the minimal and unbalanced use of external inputs. The farmers indirectly implicated the exclusive use of acid-forming inorganic fertilizers to exhaustion of the soil. Soil erosion, soil acidity, the high cost of mineral fertilizers and lime, cash shortages, and the unavailability of seeds of adapted varieties were viewed as the top ranking constraints. Species tolerance to soil acidity was found to be one of the major factors that influenced crop choice by farmers. Various land and soil characteristics, plant growth attributes, changes in genetic diversity were mentioned as indicators of soil acidity. The physico-chemical properties of the soils showed variation across land-uses and study sites. Nonetheless, the pH(H2O) of most of the soils in the study sites were in a strongly acidic range (4.6–5.5). Gashena Akayita of Banja District was the most acidic of all with high levels of exchangeable Al. At all the study sites, exchangeable Al was detected in soils having a pH of less than 5.0. Among the land-uses, eucalyptus fields were the most acidic followed by crop outfields and grazing lands, in that order. Mn toxicity was found to be a potential problem for the Districts of Enguti and Enerata. Farmers’ perceptions of soil acidity were in agreement